Simple acrylic window for a 5 gallon bucket lid. Used as a window for a cooling tank for a 40 watt laser cutter with a submersible water pump. Holes are for 4-40 screw. I used some 1/2" long flat head sheet metal screws that were lying around and used a counter syncing bit to make it flush.
Would have cut the hole out of the lid but it didn't fit in the laser cutter. Included the dxf for it in case anyone was interested.